It depends!

For one thing - never throw the solutions into your septic system! They will kill the bacteria that works on your wastes. If if they contain nothing more than salt, dont do it. First, neutralize the solution to a 6.5-7.0 using Baking Soda or Soda Ash. Then dump it. However, in spite of many of the chemicals being safe to dump - keep in mind that almost all solutions may contain salt, and salt has a bad habit of killing plant growth where you dump it. So - many of my customers tell me they simply dump their solutions on their driveways, or they dump them in a holding tank and have it pumped away and disposed of.